A vehicle including a radar system for detecting an object ahead of the vehicle (e.g., a front-running vehicle or a fallen object on a road) is well known.
For example, JP-A-2009-217495 describes a structure in which a millimeter wave radar usable even in fog or when it is raining or snowing is used as the foregoing radar system.
Further, JP-A-2001-260777 describes a structure in which a laser radar is placed beside a lighting device unit inside a lighting chamber of a headlamp.
Moreover, JP-W-11-504756 describes a structure in which an antenna module of a microwave radar and a dielectric lens are incorporated into a lighting device unit of a headlamp.
The headlamp described in JP-A-2001-260777 may alternatively have a structure in which a millimeter wave radar is placed inside the lighting chamber instead of the laser radar.
However, in such a case, the millimeter wave radar may be seen directly through a translucent cover of the headlamp, and therefore, the appearance of the headlamp may be degraded. In addition, a placement space for the millimeter wave radar has to be ensured inside the lighting chamber, thus making it difficult to make the headlamp compact in size.
On the other hand, when the lighting device unit described in JP-W-11-504756 has a structure in which an antenna module of a millimeter wave radar is incorporated into the lighting device unit, an electromagnetic lens for millimeter waves has to be placed together with an optical lens. Thus, such a lighting device structure may be complicated.